[admin] Priority APIs section renamed to Active work on the DAP home page

Hi,

To clear up confusion, I renamed the 'Priority APIs' section to 'Active work' on the DAP WG home page:

  http://www.w3.org/2009/dap/

The Priority APIs definition agreed in 2009 was no longer relevant and just caused confusion among people new to the work of this WG. The definition of 'active' I used is a spec that has an active editor, thus the Contacts API was moved to 'Other'.

-Anssi